A melt pump was assembled into the compounding line to ensure both sufficient time for diffusion process of polymer chains into the silicate gallery and sufficient mechanical shear energy for exfoliation of clay layers. The melt pump in front of the open co-rotating twin-screw extruder controls the throughput rate and the residence time, whereas the screw speed and screw geometry in the extruder determine the mechanical shear energy applied on the compound. Due to melt pump employment, the melt in metering zone can be accumulated, which results in higher mixing efficiency. It was found that using the melt pump leads to up to two times higher residence time and, consequently, higher level of material reinforcement as investigated by extensional rheology. Different melt pump adjustments, screw geometries, and screw speeds were tested and their effect on processing characteristics and material reinforcement was investigated. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 1422-1428, 2009